164. A person standing requires a space 20"X20". What are the dimensions of a square platform large enough to hold 75 people, allowing 1 ft. extra all around the edge?

165. What will be the length of a brace cut for 6 ft. run and 6 ft. rise?

166. Fig. 39 shows a roof for a lean-to. The run is 13 ft. and the rise is 6 ft. Find the necessary length of a 2X4 rafter allowing 12" for overhang and 6'' for trimming. What length of 2X4 would you order?

15'6"

18'0"

-21'0"

Fig. 40.-Scissors Roof Truss.

167. What will be the length of a rafter for 12 ft. run and 10 ft. rise allowing about 4" for trimming and 2 ft. for overhang?

168. Fig. 40 shows a scissors roof truss and the diagram to the right gives the dimensions. What is the length of the main rafter A and what is the length of the strut B?

169. Fig. 41 shows the stringer for a flight of stairs. What is the length of the stringer?

170. Fig. 42 shows a queen-post truss and the diagram to the right gives the dimensions on the center lines. Find the missing dimensions which are indicated by letters.

171. A circular platform has an area of 2402 sq.ft. What is its diameter?

172. What is the area in square inches of a circle two feet in diameter?

173. A circular window opening is 54" in diameter. How many square feet of glass surface does it contain?

174. What is the capacity of a circular cistern 5 ft. in diameter and 8 ft. deep? Give the answer in barrels.

10'0"

12'8"

Fig. 41.-Stringer for a Flight of Stairs.

175. A hot-water tank for an apartment house is said to hold 100 gallons. It is 22" in diameter and 60' high. Does it hold 100 gallons as stated? If not, what is its capacity?

-10-8"

-24'0"

Fig. 42.—Queen-post Truss.

176. A circular cistern is 5' 6'' in diameter and 10' deep. How large must a square cistern be built of the same height to contain the same amount of water? Why are cisterns usually built round instead of square?

177. A 40-gallon tank is 18'' in diameter. How high must it be?

178. A concrete silo is 16 ft. in diameter and 30 ft. high. What is its capacity in cubic feet?

179. Silage weighs about 40 lbs. per cubic foot. How many tons of silage will the above silo hold?

180. What must be the height of a circular silo to hold 10,000 cu.ft. if its diameter is 18 ft.?

181. What must be the diameter of a drain tile into which one 4"' and one 6" tile empty? The large tile must have an area equivalent to the two small ones.

CHAPTER XII

FLOORING.

LUMBER TERMS AND DIMENSIONS.

SHINGLES.

121. Lumber Trade Customs. Our methods of grading and measuring lumber are the result of custom and these customs vary somewhat in different localities.

The sizing and grading of lumber is regulated by the various lumber manufacturers' associations. Some of the terms and customs are of such wide usage that they may be explained here.

122. Lumber Terms. The term timber is generally applied to sticks more than 4" in thickness the smaller way, and the term lumber is applied to sticks less than 4" in thickness. A plank is a piece from 11" to 4" thick; while a board is a piece less than 11"' in thickness. A scantling is a piece of lumber 4"x6" in size or less. The term is most frequently applied to a 2" X 4'' stick, though it may refer to a 4"x4" or 2" X 6'' stick equally well.

Rough stock means lumber that is sawn so as to admit of dressing but that is not dressed. Dressed stock means lumber that has been planed or surfaced on one or more sides. S. 1 S is an abbreviation for “surfaced on one side." S. 2 S. means surfaced on two sides,” S. 1 S. 1 E. means

surfaced on one side and one edge” and S. 4 S. surfaced on four sides."

Dimension Lumber is usually dressed on one side and one edge in order to size it. Finishing lumber is lumber

means

intended for interior or exterior finishing. It is dressed on one or both sides or as directed.

123. Allowance for Dressing. In planing or dressing a board about ' is removed for each surface dressed. Lumber

which has not been thoroughly dried and seasoned before being dressed will shrink sufficiently to cause considerable reduction in the width of a board. A board which is nominally one inch in thickness which has been dressed on one or both sides will measure actually about 13" in thickness. If lumber is wanted to full dimensions after it is dressed,